1. Field of the Invention
The present invention relates to an electronic image recording or reproducing apparatus or a method thereof, and more particularly to an electronic image recording and reproducing apparatus or a method thereof capable of recording and reproducing with a high speed an image having a high pixel density without deteriorating image quality.
2. Description of Related Art
A recent development of digital technique has brought a use of an electronic still camera instead of a photograph using silver salt. The electronic still camera does not necessitate a wet developing processing and processing in a darkroom, which is different from a silver salt photograph. The electronic still camera has various characteristics such as simple image processing or simple data transfer, whereby it has been rapidly popularized to be used for a communication to a remote place, inputting an image to a computer, inputting to a television for domestic use or the like. The electronic still camera is provided, as an image sensing apparatus, with an optical system having a lens and an image sensing device which is used instead of a film. A CCD (charge coupling device) solid image sensing device is used as the image sensing device to store the output in a memory or to data-transfer the output to a computer to perform image processing, to thereby be displayed on a CRT (cathode ray tube) or to output the image as a hard copy.
However, in order to obtain an image quality the same as that of a conventional silver salt photograph by using a two-dimensional CCD solid an image sensing device, necessary pixel number is ten million to forty million, which is one hundred to several hundred times as many as image pixels of a conventional digital still camera. Therefore, such a camera becomes expensive and is used for only a particular purpose. In the case of using the two-dimensional CCD solid image sensing device of high pixel as described above, it is possible to perform the picking up of an image with one shot same as the case of the silver salt photograph. However, the amount of data is huge, so that it takes several to ten minutes to read data. Accordingly, continuous image sensing of a subject cannot be performed. Moreover, a memory of large capacity such as a hard disc for storing data can memorize only one image, thereby entailing a problem of requiring a large-scale apparatus in the case of picking up several images as well as a problem of taking a long period for a transfer to a remote place.
On the other hand, there is a method to read an image with a scanning operation by using one-dimensional CCD solid image sensing device in order to solve the problem of high cost. In this case, several thousand pixels of the CCD are enough, to thereby be capable of rendering the apparatus low-cost. However, it is impossible to pick an image up in one shot like the silver salt photograph or two-dimensional CCD, and further, there is a problem that a continuous image picking up cannot be performed. Moreover, the amount of data to be processed is huge, thereby the problem remains the same as that in the case of the two-dimensional CCD with reference to a memory or transferring period.
It has been known that a spatial light modulating element is used for the image picking up of a subject in order to reduce a data transferring amount. The spatial light modulating element is mainly used as an optical element for executing an optical calculation such as an extraction of an outline and may be used for a stationary picture and motion picture.
In the case of converting a natural image to a characteristic image of a natural picture in the stationary picture, there may be the case where a logical operation such as a logical sum or logical product is optically performed.
With respect to the motion picture, it is considered to compress the motion picture information by using the spatial light modulating element for transferring the motion picture information of a predetermined frame in a predetermined period, which aims to express, as for the subjective image moving in a high speed, the image data at a predetermined time by a difference of data with respect to data having an equal predetermined resolution all over the pixels at a basic time. The data amount to be transferred can be proposed since image information is compressed by the difference of data. The outline formed by the spatial light modulating element is used for determining the area of the difference of data. The resolution of the difference of data is areally constant, i.e., constant with respect to area, and is the same as the resolution of data at the basic time.
Accordingly, a still camera using a two-dimensional CCD with approximately one million pixels is considered to be of a large pixel number type among electronic still cameras to generally be used. However, in the two-dimensional CCD with the pixels as described above, the outputted image is rough and image quality is degraded, with the result that the use thereof is limited to an image output of a small size or to a display apparatus with less pixel. When the two-dimensional CCD with the pixels as described above is used for an output of a large size, the image quality is unfavorable compared to the output of a small size, with the result that it can only be used for a special purpose such as for utilizing real-time operation or image processing.